Can brain scientists read your mind?

This is a grid of numbered electrodes, with many contacts on the brain. Each contact is like a "spying microphone" capturing the activity of hundreds of thousands of cells, says Dr. Josef Parvizi.

What are you thinking about? You wouldn’t always want the answer to that question available to others, but science may be heading in that direction.

For now, researchers are far from being able to tap into your thoughts. But a new study shows how, just by looking at brain activity, it may be possible to see whether or not you’re thinking about numbers.

“The patient doesn’t need to talk to you. They can think about numbers and you can see that red mark (corresponding with activity in a particular brain region) go up,” said Dr. Josef Parvizi, associate professor of neurology at the Stanford University Medical Center and senior author of the study. The study is published in the journal Nature Communications.

Take note, this study was done on only three people with uncontrolled seizures — that’s a tiny sliver of humanity. But Parvizi said most studies on patients with intracranial electrodes only involve two to five participants, since recruitment is so difficult.

These patients had electrodes implanted in their brains to locate the source of their seizures. Surgeons perform this procedure to isolate or remove the area where seizures begin.

The researchers used these electrodes that had been implanted for locating seizures to investigate brain activity in relation to thinking about numbers, particularly in the parietal lobe. In previous studies, this brain area has been shown to be important to a person’s ability to do numerical calculations.

In one part of the experiment, patients looked at a computer screen while lying down and responded to prompts regarding the accuracy of statements. They would press “one” if the sentence or mathematical equation were correct, “two” if incorrect.

Each time a patient would perform a calculation, a group of neurons in the parietal lobe — specifically a region called the intraparietal sulcus — was very active, Parvizi said.

In another part of this study, researchers used a computer to trace the activity of the same group of neurons in the patients in an unconstrained setting. They recorded conversations between patients and experimenters, and juxtaposed the brain activity data to show the correlations between spiking activity in the math-related brain region and quantitative statements that patients made.

When patients were seeing, thinking or talking without a script, it seemed that the natural activation in the parietal lobe tended to occur right before they said something quantitative, Parvizi said. It didn’t happen every time, of course; more research would be needed to verify these findings.

Oxford University researcher Roi Cohen Kadosh called this “an innovative study that shows a nice relationship between neuronal activity during experimental setting and everyday situations.” But he pointed out that it is unclear whether the same results would be seen in healthy people, whose brains had not experienced seizures. Other studies have found multiple brain areas related to numerical understanding.

The bottom line: Just by looking at the data about brain activity, it may be possible to know when a person was thinking about numbers.

This is much simpler than trying to decode more specific thoughts from brain activity patterns. There’s no way for scientists to know if you are daydreaming about hiking with your romantic partner, worrying about finishing a big project or making a grocery list.

“We are light years behind in doing such a thing. There is absolutely no way for us to kind of record what exactly the patient is thinking because that needs a lot of complicated decoding,” Parvizi said.

Instead, this study presents a method of studying brain activity in order to get a general sense of what a person is experiencing through thoughts.

“Of course, it’s just a matter of time (before) you’re going to be able to decode brain activity in very complex conditions, such as thinking,” Parvizi said.